The related applications describe and claim a power supply controller, and various features thereof, which can be used for controlling a plurality of isolating power supplies, such as switch mode power supplies or DC power converters, for providing controlled electrical power to loads. For example, the power supplies may provide different supply voltages to various electrical circuits on a circuit card on which the power supply controller is also provided.
In such a power supply controller, separate IC (integrated circuit) control units can be provided on the primary and secondary sides of a transformer that serves to maintain an electrical isolation barrier between input and output sides of the isolating power supplies. The transformer conveniently provides for signal coupling, desirably in both directions, between the control units, and conveniently also provides for power transfer from its primary to its secondary side to supply operating power to the control unit and to any related circuits (for example, a non-volatile memory) of the power supply controller on the secondary side of the transformer.
It is desirable for such a power supply controller to be implemented in a small package, for example a surface mount package of the order of 27 mm square and 3.5 mm high; this requires that the transformer itself be very small. Although the total power required by the circuits on the secondary side of the transformer may be relatively small, it is still desirable to maximize the efficiency of the power transfer arrangement and to minimize losses of power transferred via the transformer. In addition, it is necessary to provide a desired coupling of signals in both directions via the transformer, while meeting requirements for appropriate signal levels and timing on both the primary and secondary sides of the transformer. Furthermore, the control units may operate asynchronously to one another, in which case the coupling arrangement is required to accommodate asynchronous signalling between the control units.
Accordingly, there is a need to provide signal and power transformer coupling arrangements which can facilitate meeting these considerable requirements.